The roles of epithelial cell derived type 2 initiating cytokines in experimental 1 allergic

22 Purpose: To clarify the possible involvements of type 2 initiating cytokines, interleukin 23 (IL)-25, IL-33, thymic stromal lymphopoietin (TSLP) for the pathophysiology of 24 allergic conjunctivitis, we evaluated ragweed (RW)-induced experimental allergic 25 conjunctivitis (EAC) models using IL-25 knockout (KO), IL-33 KO, TSLP receptor 26 (TSLPR) KO mice. 27 Methods: IL-25 KO, IL-33 KO, TSLPR KO and BALB/c wild type mice were 28 sensitized twice with RW in alum, and then challenged with RW in eye drops. The 29 clinical scores and eosinophil infiltration were evaluated. Serum IgE and cytokine 30 expression in the conjunctival tissue were quantified and immunohistochemical analysis 31 was carried out. 32 Results: Significant reductions of the clinical scores and the numbers of infiltrating 33 eosinophils were observed in the RWEAC models using IL-33 KO mice. There were 34 no significant differences in the clinical scores and the numbers of infiltrating 35 eosinophils among IL-25KO, TSLPR KO and wild-type mice. Serum IgE concentration 36 was upregulated after RW challenges, and there were no differences among the mouse 37 genotypes. Il4, il5, il13 and ccl5 mRNA expression was diminished in the conjunctivae 38 of RW-EAC models using IL-33 KO mice compared to those of wild type mice. IL-33 39